1. Field of the Invention
The invention relates in general to a computer system and a power management method thereof, and more particularly to a computer system whose central processing unit does not support hyper transport bus and a power management method thereof.
2. Description of the Related Art
Power management is a very important function in a computer system, and particularly in a notebook computer. Notebook computer is portable and greatly relies on the battery to provide the necessary electricity Therefore, the duration of stand-by time and the battery efficiency under limited power supply depend on the performance of power management in the computer system.
After the computer system is started up and is in an idle state, the power management function removes part of the power supplied by the computer system so as to reduce power consumption and achieve power saving. With the growth in environmental awareness, the power management system is now applied not only to the notebook computer but also to the desktop computer and different system platforms. Thus, how to enhance the function of power management has become a hot issue.
Currently, the computer system mainly adopts advanced configuration power interface (ACPI). Examples of the ACPI protocol include stand-by states S1˜S5 and power-saving states C0, C1, C2 and C3 that support the central processing unit (CPU). The state C0 denotes that the CPU is in a working state; the state C1 denotes that the CPU is in a halt state; and the states C2 and C3 denote the stand-by state controlled by the operating system. Of the above power-saving states of the CPU, the numeric number implies the performance in power saving, that is, a larger number implies more power is saved, but the time delay for the CPU to restore the working state from the power-saving state is longer in the mean time.
However, if power management is applied to different devices in the computer system, the devices need to be connected to respective power management signal lines to receive the power management signal outputted from the computer system. Consequently, electro-magnetic interference will occur among the power management signal lines.
Similarly, since the devices need to be connected to respective power management signal lines, when the power management signal lines are disposed on the printed circuit board (PCB), the large number of signal lines will make the layout of the signal lines even complicated land difficult.